1. Technical Field
The present invention relates to an image processing technology, and more particularly to an image processing technology performed using a plurality of compression image data.
2. Related Art
Recently, reduction of use volume of memory included in an image processing device has been demanded with increase in image quality of images to be processed or for other reason. For example, U.S. Pat. No. 6,115,507 discloses an image processing technology which performs DPCM (differential pulse code modulation) encoding for inputted images, stores compression image data in local memory, and decodes the data in the local memory at the time of data output so as to reduce use volume of memory (see JP-A-2003-84738 as well).
According to the technology shown in U.S. Pat. No. 6,115,507, however, all compression data in a source frame is decoded from the top of the data to extract necessary data at the time of writing a part of a compressed frame to another frame. Then, all compression data in a destination frame is decoded from the top of the data to write the extracted data to decode data in the destination frame. Finally, the decode data in the destination frame is compressed. Thus, the process requires extremely complicated operation and long time. This problem arises not only from the DPCM method but also from various types of compression technology employed for image processing devices.